This application relates to a rig including a speaker, and a measurement system.
Integrally bladed rotors (“IBRs”) are known, and typically include a hub with a plurality of airfoil blades extending outwardly of the hub. These IBRs are often utilized in gas turbine engines as part of the fan section, and sometimes the compressor and even turbine sections.
It is important to test the IBR to ensure that it is properly constructed. As an example, IBRs may experience different blade dynamic response in an engine due to a variety of phenomena.
One particular phenomena is called mistuning, and comes about due to a difference in blade-to-blade geometries and frequencies when system energy is coupled through the IBR structure and shared unequally by the airfoils of the IBR. It is known to have a traveling wave evaluation system that moves a laser vibrometer to predefined spots on the airfoil while exciting the IBR in conditions that would be relevant to engine operation via an array of speakers. Vibrometer data is then utilized to assess the IBR mistuning risk prior to accepting an IBR as a quality control measure, and also initially to approve a design of a new IBR product configuration.
The current system utilizes a “on-axis” vibrometer system. An IBR is rotated about an axis of rotation, and in the vision path of a vibrometer located over that rotational axis. The laser has mirrors that allows movement of its beam about the tips of blades on the IBR. The beam is positioned on the tip of a blade. A speaker is moved under that blade, and a sound energy is applied to one blade. The laser then indexes to measure every other blade, based upon the sound energy put into each blade. Reflective tape is positioned on each blade to provide a target for the laser.
While the above system works well for large IBRs, smaller IBRs raise challenges, and in particular, might have responses at higher frequencies and require greater measurement accuracy. In addition, the surface preparation, such as the tape, is somewhat burdensome.